Different types of processing equipment, particularly those used in waste water treatment, involve settling tanks and the like wherein a slurry consisting of a carrier liquid and suspended solids is introduced into the piece of equipment. The suspended solids are allowed to settle to the bottom of the tank into which the slurry is introduced. The solids tend to settle along a gradient with the solids"" concentration as well as composition changing as the bottom or floor of the tank is approached. Typically, the density of solids is highest at the bottom of the tank and then progressively falls towards the surface of the slurry. The quality and consistency of this solids layer and the manner in which the solids density progressively increases towards the bottom of the tank, has a bearing on how the solids layer will be subsequently processed.
For example, in large settling tanks that employ rake arms and pumping systems to draw off the solids layer, the denser the layer, the more power required by the pump and potentially the larger the pump needs to be. Accordingly, a reliable indication of the consistency and manner in which the solids have settled to the bottom of a given receptacle is required to not only size any down stream process equipment but also to appropriately operate any process equipment. For example, if the solids layer is removed too quickly, the clarified carrier liquid will also be drawn off, or if, on the other hand, the material is removed too slowly, then the density of the solids may become too great for the downstream equipment to handle.
Efforts to accurately measure the quality of the solids layer at the bottom of a container have proven difficult because placement of the measurement device, as well as the type of measurement device, have in general not been accurate enough. Based on the foregoing, it is the general object of the present invention to overcome the drawbacks and problems associated with known prior art solids profile measurement systems.
It is a more specific object of the present invention to employ an accurate sensing device in conjunction with a precise positioning mechanism in order to obtain consistent and reliable solids profile consistency data.
The present invention is directed to a solids profile measurement system for determining the quality of a solids bed formed from a liquid-solid slurry along a lower surface of a vessel containing the slurry. In general, the vessel will form part of a piece of processing equipment for handling the slurry, with said measurement system including a sensor adapted to generate signals indicative of a profile as measured by progressively immersing the sensor deeper into the slurry. The profile is formed by solids settling out of the slurry towards a bottom surface of the vessel. The solids establish a gradient between the bottom surface and the upper surface of the slurry. Extension means are provided wherein at least a portion of which is coupled at one end to the processing equipment and at an opposing end to the sensor. The extension means affect retrograde movement in a first direction, thereby immersing the sensor into the slurry. The extension means can also move the sensor in a second direction opposite to the first direction. A controller is in communication with the extension means and the sensor for issuing commands thereto and receiving signals generated by the sensor. In the preferred embodiment of the present invention, the extension means is also moveable back and forth across the vessel in response to commands issued from the controller in order to map the entire solids profile.
Preferably, the above-described extension means includes a pantograph mechanism having the sensor attached at one end thereto. Drive means, in communication with the pantograph mechanism, cause the mechanism to move the sensor in the first or second directions in response to commands issued from the controller. The drive means may include a cylinder having a rod slidably mounted therein and attached at an end thereof to the pantograph mechanism. The rod is moveable between an extended and retracted position, thereby causing the pantograph mechanism to move in the first and second directions. The cylinder can be either pneumatic or hydraulic; however, the present invention is not limited in this regard.
In an embodiment of the present invention, the extension means instead of the above-described pantograph mechanism includes a rod having the sensor coupled at one end thereto and an actuator coupled to a support that extends across the vessel. The rod and actuator communicate with one another such that the actuator moves the rod between a raised and lowered position in response to commands issued from the controller. It is preferable that the rod and actuator also be moveable back and forth along the support that spans the vessel, thereby allowing complete mapping of the solids profile. In addition, it is further preferable that the actuator be a stepper-type motor responsive to commands issued from the controller; however, the present invention is not limited in this regard.
In yet another embodiment, the extension means takes the form of a reel rotatably coupled to a mounting bracket that is in turn mounted to the particular piece of processing equipment that includes the vessel having the liquid-solid slurry contained therein. A length of flexible cable is wound about the reel and has the sensor coupled to an end thereof. An actuator is attached to the reel for rotating the wheel and causing the flexible cable, and thereby the sensor, to move in the first or second direction. The cable is positioned over a sheeve, also coupled for rotation to the mounting bracket and having an optical encoder in communication with the sheeve. During operation, the rotary encoder generates signals indicative of the number of rotations of the sheeve, said signals being receivable by the controller and thereby converted into a linear distance traveled by the sensor into or out of the slurry.